In the formation of semiconductor lead frames for mounting integrated circuit chips, the chips are bonded to pads on lead frames and after lead wires are bonded to the chip terminals and the proper leads of the frame, the chips and lead wires are encapsulated in a housing by a molding operation. Following the molding operation, the lead frame is directed through another machine where portions of the frame, known as dam bars, are punched outwardly and thereby removed. These dam bars are provided initially for supporting the leads of the frame as the frame is produced, yet the dam bars must be removed to electrically isolate the frame leads from each other. The dam bars are directed through a die machine where the dam bars are punched out of the frame.
In the molding step for encapsulating the chips on the frame, small lateral projections on the sides of the molded housings are formed, these projections being identified as flashing. These projections become a problem when the lead frame is subjected to the the dam bars therefrom. These flashed projections form particles which accumulate in the die machine for removing the dam bars and eventually jam the machine, eventually making it substantially impossible to operate the die machine. Thus, it is important for uninterrupted production of lead frames to minimize or eliminate this problem if at all possible.
Attempts in the past to eliminate the flashing projections have been made but have not been satisfactory for one or more reasons. Generally, the apparatus for accomplishing this purpose has been massive in size, requires a considerable amount of space, and is hydraulically or pneumatically driven, thereby giving rise to loud noises in the operation of the apparatus. Also, the capital equipment costs for conventional apparatus of this type is extremely high so that the protection costs of lead frame is correspondingly great.
Because of the foregoing drawbacks, a need exists for improvements in the means and techniques for removing the flashing from lead frames before the lead frames are subjected to a dye cutting operation to remove the dam bars therefrom. The present invention satisfies this need.